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prometheus/tsdb/head_wal.go

389 lines
11 KiB

// Copyright 2021 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package tsdb
import (
"fmt"
"math"
"runtime"
"sync"
"time"
"github.com/go-kit/log/level"
"github.com/pkg/errors"
"go.uber.org/atomic"
"github.com/prometheus/prometheus/pkg/exemplar"
"github.com/prometheus/prometheus/storage"
"github.com/prometheus/prometheus/tsdb/record"
"github.com/prometheus/prometheus/tsdb/tombstones"
"github.com/prometheus/prometheus/tsdb/wal"
)
func (h *Head) loadWAL(r *wal.Reader, multiRef map[uint64]uint64, mmappedChunks map[uint64][]*mmappedChunk) (err error) {
// Track number of samples that referenced a series we don't know about
// for error reporting.
var unknownRefs atomic.Uint64
var unknownExemplarRefs atomic.Uint64
// Start workers that each process samples for a partition of the series ID space.
// They are connected through a ring of channels which ensures that all sample batches
// read from the WAL are processed in order.
var (
wg sync.WaitGroup
n = runtime.GOMAXPROCS(0)
inputs = make([]chan []record.RefSample, n)
outputs = make([]chan []record.RefSample, n)
exemplarsInput chan record.RefExemplar
dec record.Decoder
shards = make([][]record.RefSample, n)
decoded = make(chan interface{}, 10)
decodeErr, seriesCreationErr error
seriesPool = sync.Pool{
New: func() interface{} {
return []record.RefSeries{}
},
}
samplesPool = sync.Pool{
New: func() interface{} {
return []record.RefSample{}
},
}
tstonesPool = sync.Pool{
New: func() interface{} {
return []tombstones.Stone{}
},
}
exemplarsPool = sync.Pool{
New: func() interface{} {
return []record.RefExemplar{}
},
}
)
defer func() {
// For CorruptionErr ensure to terminate all workers before exiting.
_, ok := err.(*wal.CorruptionErr)
if ok || seriesCreationErr != nil {
for i := 0; i < n; i++ {
close(inputs[i])
for range outputs[i] {
}
}
close(exemplarsInput)
wg.Wait()
}
}()
wg.Add(n)
for i := 0; i < n; i++ {
outputs[i] = make(chan []record.RefSample, 300)
inputs[i] = make(chan []record.RefSample, 300)
go func(input <-chan []record.RefSample, output chan<- []record.RefSample) {
unknown := h.processWALSamples(h.minValidTime.Load(), input, output)
unknownRefs.Add(unknown)
wg.Done()
}(inputs[i], outputs[i])
}
wg.Add(1)
exemplarsInput = make(chan record.RefExemplar, 300)
go func(input <-chan record.RefExemplar) {
defer wg.Done()
for e := range input {
ms := h.series.getByID(e.Ref)
if ms == nil {
unknownExemplarRefs.Inc()
continue
}
if e.T < h.minValidTime.Load() {
continue
}
// At the moment the only possible error here is out of order exemplars, which we shouldn't see when
// replaying the WAL, so lets just log the error if it's not that type.
err = h.exemplars.AddExemplar(ms.lset, exemplar.Exemplar{Ts: e.T, Value: e.V, Labels: e.Labels})
if err != nil && err == storage.ErrOutOfOrderExemplar {
level.Warn(h.logger).Log("msg", "Unexpected error when replaying WAL on exemplar record", "err", err)
}
}
}(exemplarsInput)
go func() {
defer close(decoded)
for r.Next() {
rec := r.Record()
switch dec.Type(rec) {
case record.Series:
series := seriesPool.Get().([]record.RefSeries)[:0]
series, err = dec.Series(rec, series)
if err != nil {
decodeErr = &wal.CorruptionErr{
Err: errors.Wrap(err, "decode series"),
Segment: r.Segment(),
Offset: r.Offset(),
}
return
}
decoded <- series
case record.Samples:
samples := samplesPool.Get().([]record.RefSample)[:0]
samples, err = dec.Samples(rec, samples)
if err != nil {
decodeErr = &wal.CorruptionErr{
Err: errors.Wrap(err, "decode samples"),
Segment: r.Segment(),
Offset: r.Offset(),
}
return
}
decoded <- samples
case record.Tombstones:
tstones := tstonesPool.Get().([]tombstones.Stone)[:0]
tstones, err = dec.Tombstones(rec, tstones)
if err != nil {
decodeErr = &wal.CorruptionErr{
Err: errors.Wrap(err, "decode tombstones"),
Segment: r.Segment(),
Offset: r.Offset(),
}
return
}
decoded <- tstones
case record.Exemplars:
exemplars := exemplarsPool.Get().([]record.RefExemplar)[:0]
exemplars, err = dec.Exemplars(rec, exemplars)
if err != nil {
decodeErr = &wal.CorruptionErr{
Err: errors.Wrap(err, "decode exemplars"),
Segment: r.Segment(),
Offset: r.Offset(),
}
return
}
decoded <- exemplars
default:
// Noop.
}
}
}()
// The records are always replayed from the oldest to the newest.
Outer:
for d := range decoded {
switch v := d.(type) {
case []record.RefSeries:
for _, walSeries := range v {
mSeries, created, err := h.getOrCreateWithID(walSeries.Ref, walSeries.Labels.Hash(), walSeries.Labels)
if err != nil {
seriesCreationErr = err
break Outer
}
if h.lastSeriesID.Load() < walSeries.Ref {
h.lastSeriesID.Store(walSeries.Ref)
}
mmc := mmappedChunks[walSeries.Ref]
if created {
// This is the first WAL series record for this series.
h.metrics.chunksCreated.Add(float64(len(mmc)))
h.metrics.chunks.Add(float64(len(mmc)))
mSeries.mmappedChunks = mmc
continue
}
// There's already a different ref for this series.
// A duplicate series record is only possible when the old samples were already compacted into a block.
// Hence we can discard all the samples and m-mapped chunks replayed till now for this series.
multiRef[walSeries.Ref] = mSeries.ref
idx := mSeries.ref % uint64(n)
// It is possible that some old sample is being processed in processWALSamples that
// could cause race below. So we wait for the goroutine to empty input the buffer and finish
// processing all old samples after emptying the buffer.
inputs[idx] <- []record.RefSample{}
for len(inputs[idx]) != 0 {
time.Sleep(1 * time.Millisecond)
}
// Checking if the new m-mapped chunks overlap with the already existing ones.
// This should never happen, but we have a check anyway to detect any
// edge cases that we might have missed.
if len(mSeries.mmappedChunks) > 0 && len(mmc) > 0 {
if overlapsClosedInterval(
mSeries.mmappedChunks[0].minTime,
mSeries.mmappedChunks[len(mSeries.mmappedChunks)-1].maxTime,
mmc[0].minTime,
mmc[len(mmc)-1].maxTime,
) {
// The m-map chunks for the new series ref overlaps with old m-map chunks.
seriesCreationErr = errors.Errorf("overlapping m-mapped chunks for series %s", mSeries.lset.String())
break Outer
}
}
// Replacing m-mapped chunks with the new ones (could be empty).
h.metrics.chunksCreated.Add(float64(len(mmc)))
h.metrics.chunksRemoved.Add(float64(len(mSeries.mmappedChunks)))
h.metrics.chunks.Add(float64(len(mmc) - len(mSeries.mmappedChunks)))
mSeries.mmappedChunks = mmc
// Any samples replayed till now would already be compacted. Resetting the head chunk.
mSeries.nextAt = 0
mSeries.headChunk = nil
mSeries.app = nil
h.updateMinMaxTime(mSeries.minTime(), mSeries.maxTime())
}
//nolint:staticcheck // Ignore SA6002 relax staticcheck verification.
seriesPool.Put(v)
case []record.RefSample:
samples := v
// We split up the samples into chunks of 5000 samples or less.
// With O(300 * #cores) in-flight sample batches, large scrapes could otherwise
// cause thousands of very large in flight buffers occupying large amounts
// of unused memory.
for len(samples) > 0 {
m := 5000
if len(samples) < m {
m = len(samples)
}
for i := 0; i < n; i++ {
var buf []record.RefSample
select {
case buf = <-outputs[i]:
default:
}
shards[i] = buf[:0]
}
for _, sam := range samples[:m] {
if r, ok := multiRef[sam.Ref]; ok {
sam.Ref = r
}
mod := sam.Ref % uint64(n)
shards[mod] = append(shards[mod], sam)
}
for i := 0; i < n; i++ {
inputs[i] <- shards[i]
}
samples = samples[m:]
}
//nolint:staticcheck // Ignore SA6002 relax staticcheck verification.
samplesPool.Put(v)
case []tombstones.Stone:
for _, s := range v {
for _, itv := range s.Intervals {
if itv.Maxt < h.minValidTime.Load() {
continue
}
if m := h.series.getByID(s.Ref); m == nil {
unknownRefs.Inc()
continue
}
h.tombstones.AddInterval(s.Ref, itv)
}
}
//nolint:staticcheck // Ignore SA6002 relax staticcheck verification.
tstonesPool.Put(v)
case []record.RefExemplar:
for _, e := range v {
exemplarsInput <- e
}
//nolint:staticcheck // Ignore SA6002 relax staticcheck verification.
exemplarsPool.Put(v)
default:
panic(fmt.Errorf("unexpected decoded type: %T", d))
}
}
if decodeErr != nil {
return decodeErr
}
if seriesCreationErr != nil {
// Drain the channel to unblock the goroutine.
for range decoded {
}
return seriesCreationErr
}
// Signal termination to each worker and wait for it to close its output channel.
for i := 0; i < n; i++ {
close(inputs[i])
for range outputs[i] {
}
}
close(exemplarsInput)
wg.Wait()
if r.Err() != nil {
return errors.Wrap(r.Err(), "read records")
}
if unknownRefs.Load() > 0 || unknownExemplarRefs.Load() > 0 {
level.Warn(h.logger).Log("msg", "Unknown series references", "samples", unknownRefs.Load(), "exemplars", unknownExemplarRefs.Load())
}
return nil
}
// processWALSamples adds a partition of samples it receives to the head and passes
// them on to other workers.
// Samples before the mint timestamp are discarded.
func (h *Head) processWALSamples(
minValidTime int64,
input <-chan []record.RefSample, output chan<- []record.RefSample,
) (unknownRefs uint64) {
defer close(output)
// Mitigate lock contention in getByID.
refSeries := map[uint64]*memSeries{}
mint, maxt := int64(math.MaxInt64), int64(math.MinInt64)
for samples := range input {
for _, s := range samples {
if s.T < minValidTime {
continue
}
ms := refSeries[s.Ref]
if ms == nil {
ms = h.series.getByID(s.Ref)
if ms == nil {
unknownRefs++
continue
}
refSeries[s.Ref] = ms
}
if _, chunkCreated := ms.append(s.T, s.V, 0, h.chunkDiskMapper); chunkCreated {
h.metrics.chunksCreated.Inc()
h.metrics.chunks.Inc()
}
if s.T > maxt {
maxt = s.T
}
if s.T < mint {
mint = s.T
}
}
output <- samples
}
h.updateMinMaxTime(mint, maxt)
return unknownRefs
}